1. Field of the Invention
The present invention relates to a power converter, and more specifically relates to an adaptive sampling circuit of a control circuit of the power converter.
2. Description of the Related Art
The demagnetized voltage is utilized to generate a feedback signal for the power converter. Many prior arts had been disclosed for the detection of the demagnetized voltage of the transformer, such as “Multiple-sampling circuit for measuring reflected voltage and discharge time of a transformer” U.S. Pat. No. 7,151,681; “Causal sampling circuit for measuring reflected voltage and demagnetizing time of transformer” U.S. Pat. No. 7,349,229; and “Linear-predict sampling for measuring demagnetized voltage of transformer” U.S. Pat. No. 7,486,528. However, the complexity is the drawback of the U.S. Pat. No. 7,151,681. The disadvantage of the U.S. Pat. No. 7,349,229 is the imprecise sampling in response to the dynamic loading or the input-voltage change. The approach of the U.S. Pat. No. 7,486,528 is limited by the turn ratio of the transformer design. The present invention provides an adaptive method using “linear-predict sampling” without the limitation of the transformer design.